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N. Liu, C.F. Smith, B. Bowling, F. Jonasson, G.K. Klintworth; Macular Corneal Dystrophy Types I and II Are Caused by Distinct Mutations in the CHST6 Gene in Iceland . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5547.
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© ARVO (1962-2015); The Authors (2016-present)
To identify underlying mutations in Icelandic patients with macular corneal dystrophy (MCD) types I and II by screening the CHST6 gene.
Genomic DNA was extracted from peripheral blood leukocytes of patients with MCD and their healthy family members as well as from control individuals. Mutations in the CHST6 gene were determined by a PCR–sequencing approach. Immunophenotypes of MCD were determined by measuring antigenic keratan sulfate (AgKS) levels in serum and by an immunohistochemical study on corneal tissue.
Five additional cases with MCD type I and four families with MCD type II from Iceland were included in this study. A homozygous Ala128Val mutation in the coding region of CHST6 gene was identified in four of the five cases with MCD type I. The other person with MCD type I was a compound heterozygote for Ala128Val and a frameshift Val6fs which resulted from a 10–base pair insertion (c.15_16insATGCTGTGCG). Four of five individuals with MCD type II were compound heterozygotes for Ala128Val and Val329Leu, thus sharing the same Ala128Val mutation as MCD type I. One patient with MCD type II was homozygous for Val329Leu. An analysis of the upstream region of the CHST6 gene disclosed no upstream deletion or replacements in Icelandic patients with MCD type II.
The findings fit the haplotype analysis that we reported previously in Icelandic MCD families and indicate that different mutations in the CHST6 gene cause MCD type I and type II in Iceland.
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